The present invention relates to an epicyclic gear train, or planetary gear drive apparatus for transmitting synchronized rotation to first and second concentric shafts and for selectively controlling unsynchronized relative rotation between the first and second shafts.
A drive apparatus is required for electrically driven tool compensators for moving a tool between a working position and a retracted position in combination with gauging equipment that signals a predetermined increment of tool travel each time tool adjustment is needed. Typically, the tool is moveable radially outward and inward in response to an axial movement of a draw bar. An electric motor with a gear reducer drives a screw nut assembly connected to the draw bar so that the draw bar is moved back and forth along the longitudinal axis of the draw bar, where the direction of movement is determined by the direction of rotation of the motor. The nut is formed to a cylindrical shape and has an interior cavity with a threaded opening. The drive nut is slidably mounted within the housing cavity and a draw bar assembly is removably affixed to the nut so that the draw bar moves axially as the nut rotates. A boring bar is conventionally secured to the draw bar and is operable to provide for radial inward and outward movement of a cutting tool. A cam on the boring bar is operated in response to axial movement of the draw bar in one direction to flex a strip member and move the tool radially outwardly toward the workpiece.
The drive apparatus for known tool compensator configurations is complicated and provides only limited longitudinal movement of the boring bar and connected draw bar. If additional movement could be provided, more intricate profiles could be cut. Additional movement could also provide more efficient cutting operations by allowing multiple cuts to be simultaneously performed at different radial positions at the same time. It is desirable to provide a drive apparatus with an accurate, reliable, and repeatable positioning movement of the radially moveable body member supporting the tool.
A gear drive apparatus according to the present invention includes first and second elongate, concentric, rotatable, spindles or shafts. A planetary gear transmission drives the first and second shafts in synchronized rotation with respect to one another with a primary drive input and selectively drives the first and second shafts in unsynchronized rotation with respect to one another in response to a secondary input. A control system in communication with the primary and secondary drive inputs coordinates the primary and secondary drive inputs to selectively produce synchronized and unsynchronized rotation of the first and second shafts with respect to one another.
The planetary gear transmission can include a first planetary gear group having a first ring gear, a first sun gear positioned within the first ring gear, and a plurality of first planetary gears positioned within the first gear ring and between the first gear ring and the first sun gear. The planetary gear transmission can also include a secondary planetary gear group positioned coaxially with respect to the first planetary gear group and having a second ring gear positioned coaxially with respect to the first ring gear, a second sun gear positioned within the second ring gear and positioned coaxially with respect to the first sun gear, and a plurality of second planetary gears equal in number to the plurality of first planetary gears and positioned within the second ring gear between the second sun gear and the second ring gear. The first and second planetary gears are mounted on common individual shafts for each mated pair of first and second planetary gears. A spider cage supports the common individual shafts for each matched pair of first and second planetary gears permitting idler movement with respect to the first and second sun gears and corresponding first and second ring gears in response to rotation of one of the first and second sun gears and one of the first and second ring gears. A control circuit is in communication with a primary drive input and a secondary drive input for coordinating the primary and secondary drive inputs to selectively produce synchronized and unsynchronized rotation of the first and second sun gears with respect to one another.
A method for controlling synchronized rotation of elongate, concentric, rotatable first and second shafts according to the present invention includes the steps of driving the first and second shafts in synchronized rotation with respect to one another with a single primary drive input with planetary gear means, and selectively driving the first and second shafts in unsynchronized rotation with respect to one another in response to a secondary drive input with the planetary drive means. The method can also include the step of coordinating the primary and secondary drive inputs to selectively produce synchronized and unsynchronized rotation of the first and second shaft with respect to one another with control means in communication with the primary and secondary drive inputs.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.